The need for effective means for repairing tubeless tires, primarily for automobiles, is well known in the art, and various attempts have been made to introduce improved repair means. For example, Bubik et al. U.S. Pat. No. 4,375,231 discloses a tire repair construction and method wherein a patch is placed on the inner surface of the tire against the hole and partially forced through the hole, the remaining unfilled hole then filled with a plug from the outside of the tire, eliminating bulging at the repair site. Roberts U.S. Pat. No. 4,540,035 teaches a tire repair patch, possibly for use with a plug, with a unique seal portion reducing stress on the patch and improving its effective life. Tools and methods for repairing tire damage, such as can be found in Yeh et al. U.S. Pat. No. 4,763,546, are also well known.
Patch plugs are a combination of a patch and a plug, the two parts generally bonded together in some fashion, the patch covering the tire surface and the plug filling the hole. Patch plugs are also known in the art. In Barnes et al U.S. Pat. No. 3,996,085, a patch plug is taught having a linearly extending stem along the long axis of the patch, in a form addressed specifically to tires whose inner surface is inaccessible. Ferrara U.S. Pat. No. 5,139,840 discloses a trapezoidally shaped patch plug for use with radial-ply tire sidewall patching.
However, none of the prior art addresses a particularly acute problem in the field, that of providing a strong and lasting seal between the tire and the patch plug. While the patch portion covers the damaged area and the plug portion often fills the hole, the standard patch plug does not necessarily provide a strong seal to prevent patch plug failure. Commercially available patch plugs fill the hole in the tire, but they do not provide a strong seal around the plug to, for example, prevent water introduction and the resultant rust damage to steel belts in the tire. It is common to find a patch plug weakly bonded to a hole using heat curing of the rubber components, but this limited seal easily fails under normal conditions. Sometimes a manufacturer will go so far as to treat the plug portion with a coating to enable better bonding between the tire hole walls and the plug portion, but the solution has only limited effectiveness, as the coating does not provide a full coverage of the tire breach. Previous attempts to solve this problem include the wrapping of chemical gum around the plug portion prior to insertion into the hole, held in place by a cold-bonding cement, but this wrapped coating easily peels away from the plug, allowing water entry. Another attempt was the use of a spray-on coating, but this wears off under normal use conditions.